The present invention relates to a lithographic printing plate or other imageable plates having a coating actinically imageable by ultraviolet or visible radiation.
One type of imageable lithographic printing plate or other imageable plate is a negative-working, actinic plate which has a resin coating normally soluble in a developer and which is rendered insoluble when exposed to radiation in the ultraviolet or visible wavelength range. The plate is imaged by exposing the coating to the radiation in those areas corresponding to the image to be printed with those areas crosslinking and becoming insoluble and ink receptive.
Actinic imaging, whether it be by ultraviolet radiation or by visible radiation, can be accomplished by one of two techniques. One technique is to expose the printing plate through a film negative. The other approach is to serially scan the plate with small image spots or areas. This latter approach can be accomplished by digital laser imaging or by a method referred to as digital screen imaging which will be explained later. Although digital screen imaging is not digital imaging in the strictest sense of that term as will be explained, the term “digital” will be used herein to encompass both the digital laser imaging and the digital screen imaging which both involve imaging by serially scanning the plate with small areas or spots of the imaging radiation. In any of these imaging operations, the rate of imaging is a significant factor.